Since photographic light-sensitive materials are generally composed of an electrically insulating support and photographic layers, static charges are frequently accumulated when the photographic materials are subjected to friction or separation caused by contact with the surface of the same or different materials during steps for production of the photographic light-sensitive materials or when using them for photographic purposes. These accumulated static charges cause many problems. The most serious problem is discharge of accumulated static charges prior to development processing, by which the light-sensitive emulsion layer is exposed to light to form dot spots or branched or feathery linear specks when development of the photographic films is carried out. This phenomenon is the so-called static mark. Due to the creation of such marks the commercial value of photographic films is significantly deteriorated, and is sometimes entirely lost. For example, with medical or industrial X-ray films, the static marks may result in a very dangerous judgment or misdiagnosis. This phenomenon is a very troublesome problem, because it becomes clear for the first time by carrying out development. Further, these accumulated static charges are also the origin of secondary problems such as adhesion of dusts to the surface of films, uneven coating, etc.
As described above, such static charges are frequently accumulated when producing and using photographic light-sensitive materials. For example, during production, they are generated by friction of the photographic film contacting a roller or by separation of the emulsion surface from the support surface during a rolling or unrolling step. Further, they are generated on X-ray films in an automatic camera by contact with or separating from mechanical parts or fluorescent sensitizing paper, or they are generated by contact with or separation from rollers and bars made of rubber, metal, or plastics in a bonding machine or an automatic developing machine in a developing lab or in a camera in the case of using color negative films or color reversal films. In addition, they are generated by contact with packing materials, etc.
Static marks on photographic light-sensitive materials occurring due to accumulation and discharge of static charges increase with increases in the sensitivity of the photographic light-sensitive materials and an increase of the handling speed. Particularly, static marks are easily generated because of high sensitization of the photographic light-sensitive materials and severe handling conditions such as high speed coating, high speed photographing, and high speed automatic treatment.
In order to prevent problems caused by static charges, it is suitable to add an antistatic agent to the photographic light-sensitive materials. However, antistatic agents conventionally used in other fields cannot be used freely for photographic light-sensitive materials, because they are subjected to various specific restrictions due to the nature of the photographic light-sensitive materials. More specifically, the antistatic agents which can be used in the photographic light-sensitive materials must have excellent antistatic abilities while not having adverse influences upon photographic properties of the photographic light-sensitive materials, such as sensitivity, fog, granularity, sharpness. Further, such agents must not have adverse influences upon the film strength of the photographic light-sensitive materials (the photographic light-sensitive materials are not easily injured by friction or scratching). In addition, such agents must not have an adverse influence upon antiadhesion properties (the photographic light-sensitive materials do not easily adhere when the surfaces of them are brought into contact with each other or with surfaces of other materials). Furthermore, the agents must not accelerate exhaustion of processing solutions for the photographic light-sensitive materials and not deteriorate adhesive strength between layers composing the photographic light-sensitive materials, etc. Accordingly, the application of antistatic agents to photographic light-sensitive materials are subject to many restrictions.
One method for overcoming problems caused by static charges comprises increasing electric conductivity of the surface of the photographic light-sensitive materials so that static charges disappear within a short time, prior to spark discharging of the accumulated charges.
Accordingly, processes for improving the electrically conductive property of the support or the surface of various coating layers in the photographic light-sensitive materials have been proposed hitherto, and utilization of various hygroscopic substances, water-soluble inorganic salts, certain kinds of surface active agents and polymers, etc., has been attempted. For example, it has been known to use polymers as described in U.S. Pat. Nos. 2,882,157, 2,972,535, 3,062,785, 3,262,807, 3,514,291, 3,615,531, 3,753,716, 3,938,999, etc., surface active agents as described in U.S. Pat. Nos. 2,982,651, 3,428,456, 3,457,076, 3,454,625, 3,552,972, 3,655,387, etc., and metal oxides and colloidal silica as described in U.S. Pat. Nos. 3,062,700, 3,245,833, 3,525,621, etc.
However, many of these substances exhibit great specificity, depending upon the kind of film support or the photographic composition. Although some substances produce good results on certain specific film supports, photographic emulsions or other photographic elements, they are not only useless for preventing generation of static charges when using different film supports and photographic elements, but also have an adverse influence upon photographic properties.
On the other hand, there are many cases wherein, although they have excellent antistatic effects, they cannot be used due to their adverse influence upon photographic properties such as sensitivity, fog, granularity, sharpness, etc. For example, it has been well known that polyethylene oxide compounds have antistatic effects, but they often have an adverse influence upon photographic properties, such as increase in fog, desensitization, deterioration of granularity, etc. Particularly, in light-sensitive materials in which both sides of the support are coated with photographic emulsions, such as medical direct X-ray light-sensitive materials, it has been difficult to develop techniques for effectively providing an antistatic property without having an adverse influence upon photographic properties. Thus, the application of antistatic agents to the photographic light-sensitive materials is very difficult, and their use is often limited to a certain range.
Another method for overcoming the problems of photographic light-sensitive materials caused by static charges comprises controlling the triboelectric series of the surface of the light-sensitive materials to reduce generation of static charges caused by friction or contacting as described above.
For example, it has been attempted to utilize fluorine containing surface active agents, as described in British Pat. Nos. 1,330,356, and 1,524,631, U.S. Pat. Nos. 3,666,478 and 3,589,906, Japanese Patent Publication No. 26687/77 and Japanese Patent Application (OPI) Nos. 46733/74, 32322/76, 84712/78 and 14224/79 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application"), etc., for photographic light-sensitive materials for the above-described purpose.
However, photographic light-sensitive materials containing these fluorine containing surface active agents generally have an electrostatic property of charging in negative polarity. Accordingly, although it is possible to adapt the triboelectric series of the surface of the light-sensitive materials for each triboelectric series of rubber rollers, Delrin rollers and nylon rollers by suitably combining the fluorine containing surface active agents (having an electrostatic property of charging in negative polarity) with surface active agents having an electrostatic property of charging in positive polarity, problems still occur, because the triboelectric series of the surface of the light-sensitive material cannot be simultaneously adapted for all triboelectric series of rubber rollers, Delrin rollers and nylon rollers. That is, when such fluorine containing surface active agents are used so as to adapt for rubber, branched static marks occur due to Delrin, of which the triboelectric series is situated on the positive side as compared with the triboelectric series of rubber; and when they are used so as to adapt for Delrin, spot static marks occur due to the rubber, of which the triboelectric series is situated on the negative side as compared with the triboelectric series of Delrin.
In order to compensate for this fault, there are processes which comprise reducing the surface resistance by using high molecular electrolytes together therewith as described in British Pat. No. 1,293,189. However, they also produce adverse effects; for example, they cause deterioration of antiadhesion properties and have an adverse influence upon photographic properties. Accordingly, it is impossible to incorporate them so as to provide a sufficient antistatic property.
Further, as a method in which the dependency on various materials with respect to the triboelectric series is small, fluorine containing cationic surface active agents are utilized as described in U.S. Pat. No. 3,850,642, Japanese Patent Application (OPI) Nos. 52223/73 and 127974/77, etc. However, it has been found that such technique does not have good coating properties during the production of photographic light-sensitive materials.
More specifically, it is well known that the photographic light-sensitive materials are prepared by applying a subbing layer, a silver halide photographic emulsion layer, a protective layer, a filter layer, an antihalation layer and an intermediate layer, etc., to a support composed of cellulose acetate, polyester, or polyethylene laminated paper, etc. When producing photographic light-sensitive materials having this number of layers, the coating solutions must be applied in a uniform thin layer to avoid problems such as "repelling" (i.e., a very small spot which is uncoated with a coating solution), etc. Furthermore, when producing photographic light-sensitive materials, sometimes the photographic emulsions and other gelatin containing coating solutions are applied to the support at the same time to form a multilayer structure. For example, in order to produce a color photographic light-sensitive material, three or more photographic emulsion layers are formed simultaneously by continuous application. When applying a gelatin or another colloid solution to such a gelatin colloid layer, it is very difficult to obtain coating properties required for such a case as compared with the case of applying the gelatin colloid solution directly to the support. It is particularly difficult when the layer to be applied is a wet layer set by cooling just after application. Hitherto, although many fluorine containing cationic surface active agents have been used as antistatic agents, most of them have inferior coating ability, particularly in high speed applications, and they cause formation of "comets", i.e., local imperfect coating caused by insoluble substances or dusts, "repelling" and unevenness. In order to dissolve these problems, a method wherein nonionic surface active agents are used together with fluorine containing surface active agents has been disclosed in U.S. Pat. Nos. 3,775,126 and 4,013,696, etc. However, this method is useful only for specified photographic coating solutions or under specified coating conditions, and lacks wide applicability. Also, problems in photographic properties such as desensitization occur by the use of nonionic surface active agents.